BEIRUT, Lebanon — The Lebanese military moved forcefully on Monday to quell simmering sectarian tensions around the country stoked by a Beirut bombing last week that assassinated a top security official, deploying troops in the areas worst affected and issuing an unusual statement demanding that politicians work to calm their supporters.

“Tension in some areas is increasing to unprecedented levels,” read part of a statement issued by Lebanon armed forces. “We are appealing to all leaders from all political factions to be aware about expressing their positions and trying to incite popular opinion.”

In areas where armed protesters had exchanged gunfire with the military overnight, including a southern Beirut quarter adjacent to the main airport road, the army dispatched armored patrols and sought to detain those suspected of fomenting the violence.

Soldiers also moved to separate combatants in two neighborhoods in the northern city of Tripoli where sectarian tensions have repeatedly descended into exchanges of gunfire and rocket-propelled grenades since the uprising in neighboring Syria began in March 2011. Around the country, the military forces dismantled checkpoints that armed protesters were using to try to identify their sectarian rivals.

Sectarian tensions that have long simmered beneath the surface in Lebanon surged into the open after a large bombing in Beirut on Friday that killed eight people including Brig. Gen Wissam al-Hassan, the head of the country’s internal security, who was viewed as an opponent of Syria President Bashar al-Assad and supporter of the armed insurgents trying to topple him. Mr. Assad’s government, which has a history of meddling in Lebanese politics, was widely blamed for the bombing despite its denials. Gen. Hisham Jabber, a retired military spokesman, said the army, worried about the potential for destabilization, had issued the statement to warn the political class not to exploit the situation.

“The army was very clearly telling the politicians that it is enough, they cannot make political gains at the expense of the security of this country,” General Jabber said in an interview.

The army appeared to be showing more resolve than in the past in intervening to pre-emptively thwart any escalation. Emotional attacks on the Hezbollah-dominated government during the funeral orations on Sunday inspired mourners to try to storm the offices of the prime minister. Opposition leaders later appealed for calm and the demonstrators largely dispersed.

Although the civil war in Syria next door deepened tensions between Lebanon’s Sunni and Shiite communities, Lebanon has largely avoided any explosion over the last 19 months that might reignite the civil war that wrecked this country from 1975 to 1990.

The ambassadors of Britain, the United States, Russia, China and France and the United Nations special coordinator for Lebanon met with President Michel Suleiman on Monday to express support for the efforts to keep the civil war in Syria from spilling into Lebanon.

Photo

Government forces and protesters clashed in Beirut on Sunday after the funeral of Brig. Gen. Wissam al-Hassan, who was killed by a car bomb.Credit
Maya Alleruzzo/Associated Press

"The permanent members at the United Nations call upon all the parties in Lebanon to preserve stability," Derek Plumbly, the U.N. representative, told reporters in Arabic while surrounded by the five ambassadors, The Associated Press reported. "We strongly condemn any attempt to shake Lebanon’s stability."

In Washington, a State Department spokesman, Mark Toner, said that an FBI team was headed to Lebanon to assist the Lebanese government with an investigation into the Friday bombing, which destroyed a street in the heart of Christian east Beirut and was one of the worst attacks here in years.

Mr. Toner also said Secretary of State Hillary Rodham Clinton, in a telephone call to Prime Minister Najib Mikati on Sunday, had assured him of “our firm commitment to Lebanon’s stability, its independence, its sovereignty and its security.”

The Hezbollah-dominated government is ordinarily hostile to Washington, which regards Hezbollah, the Shiite militant group, as a terrorist organization, But Lebanon’s chief of Internal Security Forces, Gen. Ashraf Rifi, confirmed in a telephone interview on Monday that judicial authorities had accepted an offer of FBI help. He said that FBI "technical experts" would arrive within 48 hours to survey the crime scene.

Lebanon’s jittery composure throughout the long Syrian uprising wobbled on Sunday, as political and religious leaders quelled street protests that erupted after the emotional funeral for General Hassan.

But later, news reports said, scattered protests and clashes continued overnight into Monday with spurts of unrest in Beirut and locations to the north and south of the capital.

After the funeral, protesters attempted unsuccessfully to occupy the Grand Serail, the Ottoman-era garrison in Beirut that houses the offices of Prime Minister Mikati, after his government was denounced at the funeral for being a puppet of Mr. Assad’s administration. Mr. Assad is close with Hezbollah, which constitutes the most powerful faction in Lebanon’s divided leadership.

An error has occurred. Please try again later.

You are already subscribed to this email.

Security forces surrounding the graceful hilltop complex sporadically lobbed tear-gas canisters and fired their guns into the air, breaking up the demonstration. Protest chants included: “Bashar al-Assad is worth as much as a shoe!” and “Hezbollah is a terrorist group!”

The sudden squall exposed the undercurrent of tension buzzing through Lebanon for much of the 19 months since the uprising began against Mr. Assad’s government. The eruption on Sunday reflected a simmering anger over the killing of Sunni civilians in Syria by allies of Mr. Assad’s Alawite sect.

Despite such outbursts and the occasional fights between supporters and opponents here, Lebanon has repeatedly inched back from the brink; leaders from all factions seem conscious that the kindling could easily fuel a conflagration.

Fouad Siniora, a former prime minister and a prominent Sunni Muslim politician, attacked the government during an angry funeral oration, saying, “The Lebanese people won’t accept, after today, the continuation of the government of assassination.”

Photo

Sons of Wissam al-Hassan at his funeral. Syria has been widely blamed for the general’s death.Credit
Ahmed Jadallah/Reuters

Within hours, he was back on the airwaves, calling for calm and condemning street protests as no way to try to replace a government. Numerous others made similar calls, including Sheik Muhammad Qabbani, the grand mufti of the Sunni Muslims, who said that “the street is not the way to solve issues.”

The main confrontation around the Grand Serail was over in less than two hours. By nightfall, only about 30 protesters were left, many of them young Syrians, vowing to camp there until the government fell. The security forces blocked off all entrances to the Serail with coils of barbed wire about two yards high.

Only minor injuries were reported from the scuffles in Beirut, but there were scattered reports of more violent episodes and Sunni-Shiite tensions elsewhere in Lebanon, including gun battles in the northern city of Tripoli, which has a standing fault line between two adjacent neighborhoods, one primarily Sunni Muslim and the other Alawite, the same main factions arrayed against each other in Syria.

Overnight, The Associated Press said, Sunni and Shiite gunmen clashed in two Beirut neighborhoods and officials reported heavy clashes late Sunday and early Monday in Tripoli and towns between Beirut and the southern city of Sidon. The officials, speaking on condition of anonymity because they were not authorized to talk to the media, said a man was killed in shooting in the Wadi Zayneh area north of Sidon and another person died in the Tripoli clashes. The officials said the clashes wounded at least six people in Beirut and 10 in Tripoli, The A.P. said.

In Damascus, Lakhdar Brahimi, the United Nations and Arab League peace envoy in Syria, met with Mr. Assad to try to arrange a short cease-fire for Id al-Adha, the feast of sacrifice that Muslims around the world will celebrate at the end of this week.

But the difficulty in stopping the violence was accented by a car bomb that went off in the square of Bab Tuma, the gateway to a storied neighborhood in the old city. The Syrian state-run news agency, SANA, put the toll at 13 killed and 29 injured, and published photos of a string of blackened vehicles that it blamed on a “terrorist” attack.

A senior Arab official, moreover, said on Monday the hope for a cease-fire was “weak.”

Ahmed Ben Hilli, deputy secretary-general of the Arab League, told Reuters that the authorities in Damascus “do not show any signs of a real desire to implement this cease-fire.” With Id al-Adha only days away, he said, “we hope the situation changes and the government and opposition respond even a little bit to this door for negotiations.”

Since the Syrian uprising began in March 2011, the Lebanese government has pursued a policy of “disassociation,” trying to maintain at least the appearance of neutrality as its neighbor’s crisis has descended into civil war.

Broadly speaking, the cabinet of Mr. Mikati, also a prominent Sunni Muslim, and his Hezbollah allies remain close to Mr. Assad’s government. The main opposition, a combination of Sunni Muslims, Druse and some Christians, has been outspoken in condemning Syria. Both Hezbollah and their staunchest foes, Sunni Muslim jihadists, have dispatched fighters to opposite sides in Syria.

Lebanese politicians of all stripes have long gotten in and out of bed with Syria. Damascus controlled Lebanon as a vassal state for some 30 years before its military and secret police were forced to withdraw in the wake of the huge protests that followed the February 2005 assassination of Rafik Hariri, Lebanon’s leading politician. Afterward, a string of car bomb assassinations like that of the security chief on Friday silenced prominent critics of Syria.

No politician of Mr. Hariri’s stature or charisma has emerged in the opposition — another reason for the anemic anti-Syria protest movement.

Cynical Lebanese also note that some politicians have sunk large investments into real estate ventures. A construction boom, perhaps the biggest since the civil war ended in 1990, is reshaping downtown Beirut into a warren of expensive apartment towers and local branches of Tiffany and Gucci, among many luxury brands. The thinking goes that the politicians do not want all the glitter to go up in flames lest they lose their investments.

Hwaida Saad, Hania Mourtada and Josh Wood contributed reporting from Beirut, Lebanon, Alan Cowell from London and Rick Gladstone from New York.